There are four languages when dealing with relational databases.
Data definition language - Defines the database schema or structure.
Data manipulation language - defines the data and how the data can be manipulated when retrieved.
Data control language - grans access to people or systems that cab carry out certain functions within the database.
Query Language - the language commands are written in in order to retrieve data, insert data, update data, or delete data from a database.
A data dictionary is where data about the data is stored. This info is often referred to as metadata. Another concept that is important to remember about relational databases is the concept of primary and foreign keys. A primary key is a unique value that no other record can posses. When you relate two tables, the primary key attribute of one table becomes the foreign key of another. This is what relates the two tables.
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